Filter presses are well known and extensively utilized for separating solids from slurries. Such presses employ a plurality of filter plates which are held in contacting relationship between fixed and movable head members while the slurry is pumped into and through the press for collecting the solid in the form of filtrate or cake between adjacent filter plates. When the press is full, then the movable head is backed away from the plates into an open position, and in one type of conventional press, the plates are then individually and sequentially moved into an open position adjacent the movable head to permit discharge of the cake which has collected between the adjacent pairs of plates. To permit movement of the plates into an open position, numerous plate shifting mechanisms have been provided for permitting either automatic or manual control over the plate movement and cake discharge.
In the known filter presses, the plate shifter mechanisms often have required various manual controls or manual manipulations associated with the movement of the plate shifter to effect sequential movement of the plates during opening thereof and dumping of the filter cake, although numerous filter press assemblies have incorporated automatic shifting mechanisms to permit such opening and dumping of the plates to be sequentially automated. Most of the automated shifter assemblies, however, have required drive mechanisms such as chains or pressure cylinders positioned adjacent opposite sides of the press, which drive mechanisms themselves are generally elongate throughout substantially the entire length of the press and hence not only increase the overall size and mechanical complexity of the press, but additionally significantly increase the overall cost of the press. These drive mechanisms are also typically disposed in areas where they are subject to contamination by the material being handled. The filter presses employing automated plate shifters have thus possessed structural and functional features which have been less than desirable.
In addition, the known filter presses have also often operated in less than a satisfactory manner when utilized with materials which result in a filtrate or cake having "sticky" properties. That is, when dealing with "sticky" cake, relying solely on gravity to cause discharge of the cake from between the opened filter plates is often insufficient to effect proper discharge since the cake tends to stick to the filter cloths or membranes of the filter plates. It has been conventional practice to manually assist the discharge by having an operator scrape the sticky cake from the filter plates by use of a paddle or the like. Needless to say, this is a very inefficient and time-consuming process. Further, satisfactory cleaning of the filter plates is difficult to achieve using this technique.
In an effort to improve the discharge of sticky cake, filter presses have been developed and sold which have employed a vibrator, one such press being manufactured and sold by Perrin of Canada. In such press, the filter plates are joined together through a control device such as a cable or linkage so that, during opening of the press, all of the plates are substantially simultaneously moved into an open separated condition with the spacing or separation between each adjacent pair of plates being controlled by the connecting linkage. All of the plates, adjacent one side thereof, are supported on an elongate tube which extends longitudinally along the press and is of square or rectangular profile. This tube is then rotated so as to impose a vibration or bouncing movement on the handles provided adjacent one side of the filter plates, whereby all of the plates are vibrated to assist in discharge of the sticky cake. While such arrangement is at least partially effective for permitting discharge of sticky cake, nevertheless this is still of undesirable structure since it requires an additional vibrating drive shaft extending longitudinally substantially throughout the length of the press, and in addition requires a long support frame or support rail arrangement since all of the filter plates are moved into an open and spaced relationship at the same time.
While it is also known to equipped filter presses with liquid washing devices for permitting cleaning of filter plates, nevertheless such devices are typically used only in a very controlled manner and in selected use situations, and typically are not used at the completion of each filter press cycle. More specifically, these washing devices typically spray water on the opened filter plates so as to permit cleaning and flushing of the filter clothes, and hence such will normally be done only infrequently, namely after a selected number of filter press cycles. Further, when such technique is used, it is typically not used to effect discharge of the filter cake since such would significantly increase the amount of liquid in the filter cake, and thus partially destroy the purpose of the filter press operation, namely the removal of liquid.
To improve upon filter presses employing a plate shifter assembly for permitting automatic and sequential shifting of filter plates into open positions during discharge of the press, the Assignee hereof has developed an improved press which is disclosed in copending U.S. Ser. No. 07/904,406, now U.S. Pat. No. 5,370,795. In the press of this latter application, the press is provide with an arch-type shifter housing which extends over and projects downwardly on both sides of the plates so that the downwardly projecting legs of the housing, adjacent lower ends thereof, are rollingly supported on the opposite elongate side rails of the press. Each of the side legs of the housing has a structure which mounts thereon a pneumatic plate shifter mechanism, and in addition one of the housing side legs mounts a pneumatic drive motor which cooperates with a stationary elongate rod which extends parallel to the guide rail to effect driving movement of the housing and shifter mechanism longitudinally along the press. The entire operation, including the movement of the housing in a steplike manner along the press, and the individual sequential shifting of the filter plates and the synchronized movement thereof with the steplike movement of the housing, is pneumatically operated, including a pneumatic logic control for controlling all of the pneumatic drive devices. The improved press of this copending application is believed to represent a desirable improvement over prior conventional structures, although the press of this prior application itself does not satisfactorily resolves the problems associated with discharge of sticky cake. However, many of the mechanisms associated with the shifter of the press of this prior application are incorporated into the present invention, and the disclosure of copending U.S. application Ser. No. 07/904,406, now U.S. Pat. No. 5,370,795, is, in its entirety, incorporated herein by reference.
Accordingly, it is an object of this invention to provide an improved filter press which is particularly desirable for use with materials which create a sticky cake or filtrate, which improved filter press greatly facilitates the discharge of sticky cake and overcomes many of the disadvantages associated with prior filter presses.
More specifically, it is an object of this invention to provide an improved filter press which incorporates devices which subject the filter plates to both a vibrating or bumping action to effect loosening of the sticky cake on the filter plates, and which thereafter subject the open filter plates to an air blow cycle to assist in discharging the sticky cake from the filter plates. The vibrating and air blow operations are preferably sequentially carried out after one of an adjacent pair of filter plates has been moved into an open position to assist in effecting downward discharge of the sticky cake from between the opened pair of filter plates, with the next filter plate thereafter being moved into an open position and the overall process being repeated between the next pair of opened plates.
It is a further object of the invention to provide an improved filter press, as aforesaid, having an improved filter plate shifting assembly which is of the arch-type so as to contain a drive associated with only one side of the filter press, without requiring driving elements extending longitudinally along both sides of the press, which arch-type shifter assembly also mounts thereon devices for effecting both vibrating and air blowing of the filter plates as described above.
It is also an object of this invention to provide an improved filter press which incorporates an air blast system which subjects the open filter plates to an air blow cycle to assist in discharging cake from the filter plates. This air blow system, in a preferred embodiment, incorporates a plurality of discharge nozzles positioned closely adjacent upper edges of the open filter plates to direct discharged high velocity air downwardly against the cake to assist in loosening and discharge of the cake, with the nozzles in the preferred embodiment being vertically displaceable downwardly along the open plates to subject the cake to discharge assisting air either continuously or at selected intervals as the nozzles vertically traverse the open filter plates. In the preferred embodiment, the nozzles discharge air at a velocity which approaches at least supersonic speed, with the nozzles having an air accumulating tank associated therewith to permit the nozzles to emit a high velocity but short duration blast of air, with several such blasts preferably being emitted sequentially at short time intervals as the nozzles traverse vertically of the filter plates.
Another object of the invention is to provide an improved filter press, as aforesaid, having a plate positioning and releasing arrangement associated with the shifter housing to ensure that the filter plate which is shifted into the open position may be disposed a predetermined distance from the closed stack of plates so that the air discharge nozzles are properly positionally related with respect to the open sides of the opposed filter plates, with the open plate then being moved any remaining distance toward the movable head of the filter press after the cake discharge operation has been completed.
Other objects and purposes of the invention will be apparent to persons familiar with presses of this general type upon reading the following specification and inspecting the accompanying drawings.